The present invention relates to thermoplastic formulations exhibiting improved physical properties such as impact strength and ductility. A block chlorinated polyolefin (b-CPO) is added to thermoplastic blends in which at least one component comprises a halogen-free hydrogen-bond acceptor polymer to achieve the desired enhancement. The synergetic effect of the b-CPO with the selected thermoplastic blend is demonstrated. Blends of thermoplastic polyurethanes (TPU), Polycarbonates (PC), copolyesters (COPE) and copolyamides (COPA) with a blend partner such as thermoplastic polyolefins (TPO), styrenic copolymers such as styrene acrylonitrile (SAN), styrene ethylene butylene styrene copolymers (SEBS), high rubber graft copolymers such as acrylonitrile butadiene styrene (ABS), methylmethacrylate butadiene styrene (MBS) and polyolefins, and the b-CPO have enhanced ductility and impact resistance. The b-CPO comprises a polymeric product having both high chlorine content blocks (e.g., up to 50-75 wt. % chlorine) and relatively non-chlorinated crystallizable polyolefin blocks. The resulting polymer is characterized as a block copolymer in that the crystallizable polyolefin blocks are covalently bonded to the amorphous chlorinated block.
Polymer blends, both thermoplastic and elastomeric, find their way into many applications because of the combination of physical properties that can be achieved. TPUs, for example, are generally formulated with other polymers in order to perform adequately for the intended use. Each component, while chosen to impart a particular advantage, is often accompanied by a corresponding undesired effect on another property. This invention relates the use b-CPOs to improve the ductility exhibited by the blend or to reduce the detrimental effect on certain properties that are observed as a result of blending. Chlorinated polyolefins, preferably conventional randomly chlorinated polyethylenes (e.g., Tyrin(copyright) from Dupont Dow Chemical) are commercially available. These chlorinated polyethylenes have been randomly (relatively homogeneously) chlorinated by using a swelling solvent and/or a chlorinating temperature above the crystalline melting temperature of the polyethylene. Traditionally, those who chlorinated polyethylene wanted to eliminate the crystalline polyethylene phase by chlorinating the crystallizable polyethylene segments, which inhibits or prevents further crystallization of the polyolefin. Residual crystalline fractions in a chlorinated polyethylene would require a processing temperature above the melting point while amorphous polyethylene fractions can be processed at a lower temperature. The use of higher chlorination temperatures and swelling solvents (which decrease residual crystallinity) also increase the rate of the chlorinating reaction, thus reducing costs. It has even been postulated that highly crystalline polyethylene would not be effectively chlorinated unless either it was heated above the crystalline melting temperature or the crystallinity was reduced by using a swelling solvent. This invention relates to the use of novel b-CPOs as additives to improve physical properties of polymer blends wherein at least one component is a polymer containing halogen-free hydrogen-bond accepting moieties such as TPUs, PCs, COPEs and COPAs etc.
Block chlorinated polyolefins (e.g., polyethylenes) can be prepared having from about 10 to about 60 wt. % preferably about 20 to about 60 wt. % bound chlorine based on the weight of the chlorinated polyolefin (e.g., polyethylene) and having from above about 25 to about 99 wt. % residual crystallizable polyolefin blocks, wherein said wt. % residual crystallizable blocks are expressed as a percentage based on the weight of crystallizable polyolefin in the polymer before chlorination. Such block chlorinated polyolefins can be prepared by a chlorination process employing a semi-crystalline polyolefin precursor comprising reacting the semi-crystalline polyolefin in a generally unswollen state at a temperature below its crystalline melting temperature with chlorine for a short period of time. Depending on the reaction conditions chosen (mostly time, chlorine pressure, and temperature), a free radical source, a catalyst, and/or UV radiation may be useful in the chlorination process. When the reaction conditions are suitable for quick chlorination, the amorphous portion of the polyolefin becomes highly chlorinated while the crystalline portion of the polyolefin remains significantly in the crystalline state.
The b-CPO, e.g., block chlorinated polyethylene (b-CPE), can allow a compounder to minimize the detrimental effect caused by the blending the selected polymers by reducing the amount of the selected blend partner required to achieve the desired level of impact or ductility. Examples of these blend partners include high rubber graft copolymers, styrenics such as SAN and SEBS, or polyolefins such as poly(propylene) (PP) and poly(ethylene) (PE). Without wishing to be bound by theory of invention, it is believed that the b-CPOs of this invention improve the adhesion between the immiscible blend partner phase and the halogen-free hydrogen-bond acceptor polymer.